Communication of point to multipoint service information in wireless communication system

ABSTRACT

The present invention relates to a method for transmitting and receiving information for configuring a point-to-multipoint control channel in a wireless communication system. A network generates configuration information for configuring a point-to-multipoint control channel (MCCH) and transmits the configuration information to a mobile terminal. The configuration information comprises at least one of a modification period, a repetition period, a SFN-MCCH-Offset comprising an offset between a transmission of a first frame of a modification period and a system frame number (SFN) of a cell in which the configuration information is transmitted, and a number of transmission time intervals (TTIs) the mobile terminal will read at each beginning of a repetition period.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. § 119(e), this application claims the benefit ofearlier filing date and right of priority to U.S. ProvisionalApplication No. 60/563,869, filed on Apr. 19, 2004, the contents ofwhich are hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to transmitting and receivingpoint-to-multipoint control information, and more particularly, totransmitting and receiving information for configuring apoint-to-multipoint control channel in a wireless communication system.

2. Description of the Related Art

Recently, mobile communication systems have developed remarkably, butfor high capacity data communication services, the performance of mobilecommunication systems cannot match that of existing wired communicationsystems. Accordingly, technical developments for IMT-2000, which is acommunication system allowing high capacity data communications, arebeing made and standardization of such technology is being activelypursued among various companies and organizations.

A universal mobile telecommunication system (UMTS) is a third generationmobile communication system that has evolved from a European standardknown as Global System for Mobile communications (GSM). The UMTS aims toprovide improved mobile communication service based on a GSM corenetwork and wideband code division multiple access (W-CDMA) wirelessconnection technology.

In December 1998, ETSI of Europe, ARIB/TTC of Japan, T1of the UnitedStates, and TTA of Korea formed a Third Generation Partnership Project(3GPP) for creating the detailed specifications of the UMTS technology.

Within the 3GPP, in order to achieve rapid and efficient technicaldevelopment of the UMTS, five technical specification groups (TSG) havebeen created for performing the standardization of the UMTS byconsidering the independent nature of the network elements and theiroperations.

Each TSG develops, approves, and manages the standard specificationwithin a related region. Among these groups, the radio access network(RAN) group (TSG-RAN) develops the standards for the functions,requirements, and interface of the UMTS terrestrial radio access network(UTRAN), which is a new radio access network for supporting W-CDMAaccess technology in the UMTS.

FIG. 1 illustrates an exemplary basic structure of a general UMTSnetwork. As shown in FIG. 1, the UMTS is roughly divided into a terminal(or user equipment: UE) 10, a UTRAN 100, and a core network (CN) 200.

The UTRAN 100 includes one or more radio network sub-systems (RNS) 110,120. Each RNS 110, 120 includes a radio network controller (RNC) 111,and a plurality of base stations or Node-Bs 112, 113 managed by the RNC111. The RNC 111 handles the assigning and managing of radio resources,and operates as an access point with respect to the core network 200.

The Node-Bs 112,113 receive information sent by the physical layer ofthe terminal through an uplink, and transmit data to the terminalthrough a downlink. The Node-Bs 112,113, thus, operate as access pointsof the UTRAN 100 for the terminal.

A primary function of the UTRAN 100 is forming and maintaining a radioaccess bearer (RAB) to allow communication between the terminal and thecore network 200. The core network 200 applies end-to-end quality ofservice (QoS) requirements to the RAB, and the RAB supports the QoSrequirements set by the core network 200. As the UTRAN 100 forms andmaintains the RAB, the QoS requirements of end-to-end are satisfied. TheRAB service can be further divided into an Iu bearer service and a radiobearer service. The Iu bearer service supports a reliable transmissionof user data between boundary nodes of the UTRAN 100 and the corenetwork 200.

The core network 200 includes a mobile switching center (MSC) 210 and agateway mobile switching center (GMSC) 220 connected together forsupporting a circuit switched (CS) service, and a serving GPRS supportnode (SGSN) 230 and a gateway GPRS support node 240 connected togetherfor supporting a packet switched (PS) service.

The services provided to a specific terminal are roughly divided intothe circuit switched (CS) services and the packet switched (PS)services. For example, a general voice conversation service is a circuitswitched service, while a Web browsing service via an Internetconnection is classified as a packet switched (PS) service.

For supporting circuit switched services, the RNCs 111 are connected tothe MSC 210 of the core network 200, and the MSC 210 is connected to theGMSC 220 that manages the connection with other networks.

For supporting packet switched services, the RNCs 111 are connected tothe SGSN 230 and the GGSN 240 of the core network 200. The SGSN 230supports the packet communications going toward the RNCs 111, and theGGSN 240 manages the connection with other packet switched networks,such as the Internet.

Various types of interfaces exist between network components to allowthe network components to transmit and receive information to and fromeach other for mutual communication therebetween. An interface betweenthe RNC 111 and the core network 200 is defined as an Iu interface. Inparticular, the Iu interface between the RNCs 111 and the core network200 for packet switched systems is defined as “Iu-PS,” and the Iuinterface between the RNCs 111 and the core network 200 for circuitswitched systems is defined as “Iu-CS.”

FIG. 2 illustrates a structure of a radio interface protocol between theterminal and the UTRAN according to the 3GPP radio access networkstandards.

As shown in FIG. 2, the radio interface protocol has horizontal layerscomprising a physical layer, a data link layer, and a network layer, andhas vertical planes comprising a user plane (U-plane) for transmittinguser data and a control plane (C-plane) for transmitting controlinformation.

The user plane is a region that handles traffic information of the user,such as voice or Internet protocol (IP) packets, while the control planeis a region that handles control information for an interface of anetwork, maintenance and management of a call, and the like.

The protocol layers in FIG. 2 can be divided into a first layer (L1), asecond layer (L2), and a third layer (L3) based on three lower layers ofan open system interconnection (OSI) standard model. Each layer will bedescribed in more detail as follows.

The first layer (L1), namely, the physical layer, provides aninformation transfer service to an upper layer by using various radiotransmission techniques. The physical layer is connected to an upperlayer called a medium access control (MAC) layer, via a transportchannel. The MAC layer and the physical layer send and receive data withone another via the transport channel.

The second layer (L2) includes a MAC layer, a radio link control (RLC)layer, a broadcast/multicast control (BMC) layer, and a packet dataconvergence protocol (PDCP) layer.

The MAC layer provides an allocation service of the MAC parameters forallocation and re-allocation of radio resources. The MAC layer isconnected to an upper layer called the radio link control (RLC) layer,via a logical channel.

Various logical channels are provided according to the kind oftransmitted information. In general, when information of the controlplane is transmitted, a control channel is used. When information of theuser plane is transmitted, a traffic channel is used. A logical channelmay be a common channel or a dedicated channel depending on whether thelogical channel is shared. Logical channels include a dedicated trafficchannel (DTCH), a dedicated control channel (DCCH), a common trafficchannel (CTCH), a common control channel (CCCH), a broadcast controlchannel (BCCH) and a paging control channel (PCCH) or a Shared ChannelControl Channel (SHCCH). The BCCH provides information includinginformation utilized by a terminal to access a system. The PCCH is usedby the UTRAN to access a terminal.

For the purposes of MBMS, additional traffic and control channels exist.For example, an MCCH (MBMS point-to-multipoint Control Channel) is usedfor transmitting MBMS control information while an MTCH (MBMSpoint-to-multipoint Traffic Channel) is used for transmitting MBMSservice data.

The different logical channels that exist are listed below:

The MAC layer is connected to the physical layer by transport channelsand can be divided into a MAC-b sub-layer, a MAC-d sub-layer, a MAC-c/shsub-layer, and a MAC-hs sub-layer according to the type of transportchannel to be managed.

The MAC-b sub-layer manages a BCH (Broadcast Channel), which is atransport channel handling the broadcasting of system information. TheMAC-d sub-layer manages a dedicated channel (DCH), which is a dedicatedtransport channel for a specific terminal. Accordingly, the MAC-dsub-layer of the UTRAN is located in a serving radio network controller(SRNC) that manages a corresponding terminal, and one MAC-d sub-layeralso exists within each terminal (UE).

The MAC-c/sh sub-layer manages a common transport channel, such as aforward access channel (FACH) or a downlink shared channel (DSCH), whichis shared by a plurality of terminals, or in the uplink the Radio AccessChannel (RACH). In the UTRAN, the MAC-c/sh sub-layer is located in acontrolling radio network controller (CRNC). As the MAC-c/sh sub-layermanages the channel being shared by all terminals within a cell region,a single MAC-c/sh sub-layer exists for each cell region. Also, oneMAC-c/sh sub-layer exists in each terminal (UE). Referring to FIG. 3,possible mapping between the logical channels and the transport channelsfrom a UE perspective is shown. Referring to FIG. 4, possible mappingbetween the logical channels and the transport channels from a UTRANperspective is shown.

The RLC layer supports reliable data transmissions, and performs asegmentation and concatenation function on a plurality of RLC servicedata units (RLC SDUs) delivered from an upper layer. When the RLC layerreceives the RLC SDUs from the upper layer, the RLC layer adjusts thesize of each RLC SDU in an appropriate manner upon consideringprocessing capacity, and then creates certain data units with headerinformation added thereto. The created data units are called protocoldata units (PDUs), which are then transferred to the MAC layer via alogical channel. The RLC layer includes a RLC buffer for storing the RLCSDUs and/or the RLC PDUs.

The BMC layer schedules a cell broadcast message (referred to as a ‘CBmessage’, hereinafter) received from the core network, and broadcaststhe CB messages to terminals located in a specific cell(s). The BMClayer of the UTRAN generates a broadcast/multicast control (BMC) messageby adding information, such as a message ID (identification), a serialnumber, and a coding scheme to the CB message received from the upperlayer, and transfers the BMC message to the RLC layer. The BMC messagesare transferred from the RLC layer to the MAC layer through a logicalchannel, i.e., the CTCH (Common Traffic Channel). The CTCH is mapped toa transport channel, i.e., a FACH, which is mapped to a physicalchannel, i.e., a S-CCPCH (Secondary Common Control Physical Channel).

The PDCP (Packet Data Convergence Protocol) layer, as a higher layer ofthe RLC layer, allows the data transmitted through a network protocol,such as an IPv4 or IPv6, to be effectively transmitted on a radiointerface with a relatively small bandwidth. To achieve this, the PDCPlayer reduces unnecessary control information used in a wired network, afunction called header compression.

A radio resource control (RRC) layer is located at a lowermost portionof the L3 layer. The RRC layer is defined only in the control plane, andhandles the control of logical channels, transport channels, andphysical channels with respect to setup, reconfiguration, and release orcancellation of radio bearers (RBs). The radio bearer service refers toa service provided by the second layer (L2) for data transmissionbetween the terminal and the UTRAN. In general, the setup of the radiobearer refers to the process of defining the characteristics of aprotocol layer and a channel required for providing a specific dataservice, as well as respectively setting detailed parameters andoperation methods.

The RLC layer can belong to the user plane or to the control planedepending upon the type of layer connected at the upper layer of the RLClayer. That is, if the RLC layer receives data from the RRC layer, theRLC layer belongs to the control plane. Otherwise, the RLC layer belongsto the user plane.

The different possibilities that exist for the mapping between the radiobearers and the transport channels are not always possible. The UE/UTRANdeduces the possible mapping depending on the UE state and the procedurethat the UE/UTRAN is executing. The different states and modes areexplained in more detail below.

The different transport channels are mapped onto different physicalchannels. For example, the RACH transport channel is mapped on a givenPRACH, the DCH can be mapped on the DPCH, the FACH and the PCH can bemapped on the S-CCPCH, the DSCH is mapped on the PDSCH and so on. Theconfiguration of the physical channels is given by an RRC signalingexchange between the RNC and the UE.

The RRC mode refers to whether there exists a logical connection betweenthe RRC of the terminal and the RRC of the UTRAN. If there is aconnection, the terminal is said to be in RRC connected mode. If thereis no connection, the terminal is said to be in idle mode. Because anRRC connection exists for terminals in RRC connected mode, the UTRAN candetermine the existence of a particular terminal within the unit ofcells, for example which cell or set of cells the RRC connected modeterminal is in, and which physical channel the UE is listening to. Thus,the terminal can be effectively controlled.

In contrast, the UTRAN cannot determine the existence of a terminal inidle mode. The existence of idle mode terminals can only be determinedby the core network. Specifically, the core network can only detect theexistence of idle mode terminals within a region that is larger than acell, such as a location or a routing area. Therefore, the existence ofidle mode terminals is determined within large regions. In order toreceive mobile communication services such as voice or data, the idlemode terminal must move or change into the RRC connected mode. Thepossible transitions between modes and states are shown in FIG. 5.

A UE in RRC connected mode can be in different states, such as aCELL_FACH state, a CELL_PCH state, a CELL_DCH state or a URA_PCH state.Depending on the states, the UE listens to different channels. Forexample a UE in CELL_DCH state will try to listen (amongst others) toDCH type of transport channels, which comprises DTCH and DCCH transportchannels, and which can be mapped to a certain DPCH. The UE in CELL_FACHstate will listen to several FACH transport channels which are mapped toa certain S-CCPCH physical channel. The UE in PCH state will listen tothe PICH channel and to the PCH channel, which is mapped to a certainS-CCPCH physical channel.

The UE also carries out different actions depending on the state. Forexample, based on different conditions, a UE in CELL_FACH will start aCELL Update procedure each time the UE changes from the coverage of onecell into the coverage of another cell. The UE starts the CELL Updateprocedure by sending to the NodeB a Cell Update message to indicate thatthe UE has changed its location. The UE will then start listening to theFACH. This procedure is additionally used when the UE comes from anyother state to CELL_FACH state and the UE has no C-RNTI available, suchas when the UE comes from the CELL_PCH state or CELL_DCH state, or whenthe UE in CELL_FACH state was out of coverage.

In the CELL_DCH state, the UE is granted dedicated radio resources, andmay additionally use shared radio resources. This allows the UE to havea high data rate and efficient data exchange. However, the radioresources are limited. It is the responsibility of the UTRAN to allocatethe radio resources amongst the UEs such that they are efficiently usedand ensure that the different UEs obtain the quality of servicerequired.

A UE in CELL_FACH state has no dedicated radio resources attributed, andcan only communicate with the UTRAN via shared channels. Thus, the UEconsumes few radio resources. However, the data rate available is verylimited. Also, the UE needs to permanently monitor the shared channels.Thus, UE battery consumption is increased in the case where the UE isnot transmitting.

A UE in CELL_PCH/URA_PCH state only monitors the paging channel atdedicated occasions, and therefore minimizes the battery consumption.However, if the network wishes to access the UE, it must first indicatethis desire on the paging occasion. The network may then access the UE,but only if the UE has replied to the paging. Furthermore, the UE canonly access the network after performing a Cell Update procedure whichintroduces additional delays when the UE wants to send data to theUTRAN.

Main system information is sent on the BCCH logical channel, which ismapped on the P-CCPCH (Primary Common Control Physical Channel).Specific system information blocks can be sent on the FACH channel. Whenthe system information is sent on the FACH, the UE receives theconfiguration of the FACH either on the BCCH that is received on theP-CCPCH or on a dedicated channel. When the system information is senton the BCCH via the P-CCPCH, then in each frame or set of two frames, asystem frame number (SFN) is sent which is used to share the same timingreference between the UE and the Node B. The P-CCPCH is sent using thesame scrambling code as a P-CPICH (Primary Common Pilot Channel), whichis the primary scrambling code of the cell. Each channel uses aspreading code as commonly done in WCDMA (Wideband Code DivisionMultiple Access) systems. Each code is characterized by its spreadingfactor (SF), which corresponds to the length of the code. For a givenspreading factor, the number of orthogonal codes is equal to the lengthof the code. For each spreading factor, the given set of orthogonalcodes, as specified in the UMTS system, are numbered from 0 to SF−1.Each code can thus be identified by giving its length (i.e. spreadingfactor) and the number of the code. The spreading code that is used bythe P-CCPCH is always of a fixed spreading factor 256 and the number isthe number 1. The UE knows about the primary scrambling code either byinformation sent from the network on system information of neighboringcells that the UE has read, by messages that the UE has received on theDCCH channel, or by searching for the P-CPICH, which is sent using thefixed SF 256 and the spreading code number 0, and which transmits afixed pattern.

The system information comprises information on neighboring cells,configuration of the RACH and FACH transport channels, and theconfiguration of MCCH, which is a channel dedicated for MBMS service.Each time the UE changes cells, it is camping or in idle mode. When theUE has selected the cell (in CELL_FACH, CELL_PCH or URA_PCH state), theUE verifies that it has valid system information.

The system information is organized in SIBs (system information blocks),a MIB (Master information block) and scheduling blocks. The MIB is sentvery frequently and provides timing information of the scheduling blocksand the different SIBs. For SIBs that are linked to a value tag, the MIBalso contains information on the last version of a part of the SIBs.SIBs that are not linked to a value tag are linked to an expirationtimer. The SIBs linked to an expiration timer become invalid and need tobe reread if the time of the last reading of the SIB is larger than anexpiration timer value. The SIBs linked to a value tag are only valid ifthey have the same value tag as a value tag broadcast in the MIB. Eachblock has an area scope of validity, such as a Cell, a PLMN (Public LandMobile Network) or an equivalent PLMN, which signifies on which cellsthe SIB is valid. A SIB with the area scope “Cell” is valid only for thecell in which it has been read. A SIB with the area scope “PLMN” isvalid in the whole PLMN. A SIB with the area scope “equivalent PLMN” isvalid in the whole PLMN and equivalent PLMN.

In general, UEs read the system information when they are in idle mode,CELL_FACH state, CELL_PCH state or in URA_PCH state of the cell thatthey have selected, i.e., the cell that they are camping on. In thesystem information, the UEs receive information on the neighboring cellson the same frequency, different frequencies and different RAT (Radioaccess technologies). This allows the UEs to know which cells arecandidates for cell reselection.

The 3GPP system can provide multimedia broadcast multicast service(MBMS). The 3GPP TSG SA (Service and System Aspect) defines variousnetwork elements and their functions required for supporting MBMSservices. A cell broadcast service provided by the prior art is limitedto a service in which text type short messages are broadcast to acertain area. The MBMS service, however, is a more advanced service thatmulticasts multimedia data to terminals (UEs) that have subscribed tothe corresponding service in addition to broadcasting multimedia data.

The MBMS service is a downward-dedicated service that provides astreaming or background service to a plurality of terminals by using acommon or dedicated downward channel. The MBMS service is divided into abroadcast mode and a multicast mode. The MBMS broadcast mode facilitatestransmitting multimedia data to every user located in a broadcast area,whereas the MBMS multicast mode facilitates transmitting multimedia datato a specific user group located in a multicast area. The broadcast areasignifies a broadcast service available area and the multicast areasignifies a multicast service available area.

FIG. 6 illustrates a process of providing a particular MBMS service, byusing the multicast mode. The procedure can be split into two types ofactions, those that are transparent and those that are not transparentto the UTRAN.

The transparent actions are described in the following. A user desiringto receive the MBMS service, first needs to subscribe in order to beallowed to receive MBMS services, to receive information on MBMSservices, and to join a certain set of MBMS services. A serviceannouncement provides the terminal with a list of services to beprovided and other related information. The user can then join theseservices. By joining, the user indicates that the user wants to receiveinformation linked to services that the user has subscribed to andbecomes part of a multicast service group. When a user is no longerinterested in a given MBMS service, the user leaves the service, i.e.,the user is no longer part of the multicast service group. These actionscan be taken by using any means of communication, i.e., the actions maybe done using SMS (Short Messaging Service), or by Internet access.These actions do not have to necessarily be done using the UMTS system.

In order to receive a service for which the user is in a multicast groupthe following actions that are not transparent to the UTRAN areexecuted. The SGSN informs the RNC about a session start. Then the RNCnotifies the UEs of the multicast group that a given service has startedin order to initiate reception of the given service. After havingbroadcast the necessary UE actions and eventually the configuration ofthe PtM bearers for the given service, the transmission of the datastarts. When the session stops, the SGSN indicates the stopped sessionto the RNC. The RNC in turn initiates a session stop. The transmissionof the service from the SGSN means for the RNC to provide a bearerservice for conveying the data of the MBMS service.

After the notification procedure, other procedures can be initiatedbetween the UE and the RNC and the SGSN to enable data transmission,such as RRC connection establishment, connection establishment towardsthe PS domain, frequency layer convergence, and counting.

Reception of an MBMS service may be performed in parallel to thereception of other services, such as a voice or video call on the CSdomain, SMS transfer on the CS or PS domain, data transfer on the PSdomain, or any signaling related to the UTRAN or PS or CS domain.

Contrary to the multicast service, for broadcast services, as shown inFIG. 7, only the announcement of the service must be done in atransparent manner. No subscription or joining is needed. Afterwards,the actions that are transparent to the RNC are the same as formulticast services.

For MBMS, two additional control channels are introduced. They are theMCCH and the MICH (MBMS Notification Indicator Channel). As explainedabove, the MCCH is mapped on the FACH. The MICH is a new physicalchannel and is used to notify users to read the MCCH channel. The MICHis designed to allow the UEs to perform a DRX (Discontinuous Reception)scheme. DRX allows the reduction of battery consumption for UEs whileallowing the UEs to still be aware of any service for which a session isstarting. The MICH may be used to inform the UE of a change in afrequency convergence scheme, change of a configuration of apoint-to-multipoint (PtM) bearer, switch between the PtM bearer and apoint-to-point (PtP) bearer, etc., which all require the MCCH to beread.

The MCCH channel periodically transmits information regarding activeservices, MTCH configuration, frequency convergence, etc. The UE readsthe MCCH information to receive the subscribed services based ondifferent triggers. For example, the UE may be triggered after cellselection/reselection, when the UE is notified of a given service on theMICH, or when the UE is notified via the DCCH channel. The MCCH carriesdifferent messages, such as MBMS Common p-t-m rb Information, MBMSCurrent Cell p-t-m rb Information, MBMS General Information, MBMSModified services Information, MBMS Neighbouring Cell p-t-m rbInformation or MBMS Unmodified services Information and MBMS AccessInformation.

The MCCH information is transmitted based on a fixed schedule. Theschedule identifies a transmission time interval (TTI) containing thebeginning of the MCCH information. The transmission of the informationmay take a variable number of TTIs. The UTRAN transmits the MCCHinformation in consecutive TTIs. The mobile terminal (UE) continues toreceive the SCCPCH until: 1) the UE receives all of the MCCHinformation; 2) the UE receives a TTI that does not include any MCCHdata; or 3) the information contents indicate that further reception isnot required (e.g. there is no modification to the desired serviceinformation).

Based on this behavior, the UTRAN may repeat the MCCH informationfollowing a scheduled transmission in order to improve reliability. TheMCCH schedule is common for all services. The entire MCCH information istransmitted periodically based on a “repetition period”. A “modificationperiod” is defined as an integer multiple of the repetition period. TheMBMS ACCESS INFORMATION may be transmitted periodically based on an“access info period”. This period is an integer divider of the“repetition period”.

MCCH information may be categorized as critical and non-criticalinformation. Changes to critical information will only be applied at thefirst MCCH transmission of a modification period. At the beginning ofeach modification period, the UTRAN transmits the MBMS Modified servicesInformation including, amongst others, information on MBMS serviceswhose MCCH information is modified at that modification period. MBMSModified services Information is repeated at least once in eachrepetition period of that modification period. Changes to non-criticalinformation may take place at any time. FIG. 8 illustrates a schedulewith which the MBMS Modified services Information and the remaininginformation sent on MCCH are transmitted. Differently patterned blocksindicate potentially different MCCH content.

An MBMS notification mechanism is used to inform UEs of an upcomingchange in critical MCCH information. Notifications on MICH are based onservice groups. Notifications might also be sent via dedicated signalingto UEs using the DCCH channel. The mapping between service IDs andservice groups are based on a hashing mechanism. The MBMS notificationindicators are sent on MICH. A single MICH frame is able to carryindications for every service group.

Critical MCCH information can only be changed at the beginning of amodification period. The MBMS notification indicator corresponding tothe service group of every affected service is set continuously duringthe entire modification period preceding the first change in MCCHinformation related to a given service. Subsequent changes in the MCCHinformation in the next modification period related to the same servicecan be signaled on the MCCH.

UEs that are not receiving any MBMS services on MTCH or on a PtP channelare free to read the MBMS notification at any time; however, themodification interval is long enough so that the UEs are able toreliably detect the notification even if they only receive the MICHduring regular paging occasions.

Upon detecting the MBMS notification indication for a service group, theUEs interested in a service corresponding to the service group startreading the MCCH at the beginning of the next modification period. TheUE reads at least the MBMS Modified services Information.

FIG. 9 illustrates the timing relationship between the setting of theMICH and the first MCCH critical information change. For the MICH, aperiod 20, designated by a diagonal pattern, indicates when aNotification Indicator (NI) is set for a service. For the MCCH,differently patterned blocks indicate MCCH content related to thenotification of different services.

UEs, which are receiving MBMS service(s) on MTCH in idle mode or in aURA_PCH, CELL_PCH, or CELL_FACH state read the MCCH at the beginning ofeach modification period to receive the MBMS Modified servicesInformation. The MBMS Modified services Information indicates, amongstothers, MBMS service IDs, and optionally, an MBMS Session ID, whose MCCHinformation is modified at a modification period. If the MBMS serviceIDs and the MBMS Session ID, which the UE has activated, is indicated inthe MBMS Modified services Information, the UE reads the rest of theMCCH information.

MBMS Counting is used to determine the optimum transmission mechanismfor a given service. The need for counting is indicated in thenotification, and achieved by requesting UEs, belonging to the same MBMSservice group, to establish an RRC connection. The exact number of UEsthat need to be brought to RRC connected mode is a Radio ResourceManagement (RRM) issue. Since it is desirable in a specific cell, toavoid bringing a large number of UEs for counting purposes to RRCconnected mode at the same time (RACH load, etc), RRM may control theload due to the RRC connection establishment requests, by setting anaccess “probability factor”.

Following counting, the number of subscribers that need to be maintainedin RRC connected mode or for which the RNC releases their connection, isalso an RRM issue. For a given MBMS service, the counting indication inthe notification may be switched on and off, on a per cell basis. TheRNC may use notification to indicate counting during an ongoing MBMSsession. The term used for this is re-counting. The RNC receives, via Iufrom the CN, information (MBMS service ID) about UEs that are in RRCConnected mode, and have joined the MBMS service. This information maybe used for counting purposes.

The MBMS counting function includes a mechanism by which the UTRAN canprompt users interested in a given service to become RRC connected. Thisprocedure is only applicable for UEs in idle mode and relies on the MBMSACCESS INFORMATION transmitted on the MCCH. The probability factorindicates the probability with which UEs need to attempt an RRCconnection procedure.

Once a UE detects that the counting procedure is ongoing for thespecific service it wants to receive, it will attempt to set up an RRCconnection based on the probability factor included in the MCCH. UEs ina URA_PCH, CELL_PCH and/or CELL_FACH state, which are notified on theMCCH, shall initiate a cell update procedure with a specific cause basedupon the information provided in the MBMS ACCESS INFORMATION.

Also, the UE will keep receiving the MBMS ACCESS INFORMATION at everyaccess info period unless the UE in idle mode becomes RRC connected, theUE in the URA_PCH, CELL_PCH or CELL_FACH state finishes the cell updateprocedure successfully, the RRC Connection Setup procedure or CellUpdate procedure are ongoing, or counting is no longer required.Whenever it receives new MBMS ACCESS INFORMATION, the UE will update itsprobability factor with the new value.

FIG. 10 illustrates the above-mentioned mechanism. For the MICH, aperiod 30, designated by a diagonal pattern, indicates when the NI isset for the service. For the MBMS ACCESS INFORMATION, the blocks havinga diagonal pattern indicate that the counting procedure is ongoing, andthat the UEs need to establish an RRC connection based on the includedprobability factor (PF). For the critical MCCH Info, differentlypatterned blocks indicate potentially different content.

For every UE brought to RRC connected state for the purpose of counting,the UTRAN will initiate a PMM Connection establishment procedure andwill obtain from the CN the set of MBMS services the users have joined.Counting for ongoing services (re-counting) will rely on the samescheduling of the MCCH information.

In order to be able to read the MCCH, the UE needs information relatedto the configuration of the MCCH. More specifically, the UE requiresinformation regarding the “Modification Period,” the “Repetitionperiod,” and the offset between the transmission of the first frame ofthe modification period and the SFN of the cell in which the informationis sent. Furthermore, the information on the MCCH can be carried in morethan one TTI. However, it is inefficient for the UE to read more TTIsthan necessary. Thus, the UE also requires information regarding thenumber of TTIs that the UE shall read.

SUMMARY OF THE INVENTION

The present invention is directed to a method for transmitting andreceiving information for configuring an MBMS control channel.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, the presentinvention is embodied in a method for transmitting control informationin a wireless communication system, the method comprising, generatingconfiguration information for configuring a point-to-multipoint controlchannel and transmitting the configuration information to a mobileterminal. The configuration information comprises at least one of amodification period, a repetition period, a SFN-MCCH-Offset comprisingan offset between a transmission of a first frame of a modificationperiod and a system frame number (SFN) of a cell in which theconfiguration information is transmitted, and a number of transmissiontime intervals (TTIs) the mobile terminal will read at each beginning ofa repetition period.

Preferably, the configuration information is transmitted from a radionetwork controller (RNC). The modification period is a time throughwhich critical information is not changed. The repetition period is atime between successive repetition of the transmission of critical andnon-critical information. The SFN-MCCH-Offset is an offset between a SFN0 and a first transmission of critical and non-critical information.

In one aspect of the present invention, the SFN-MCCH-Offset is amultiple of 256 chips and is a maximum time of a maximum modificationperiod. Preferably, the maximum SFN-MCCH-Offset is 4096 frames.

Preferably, the configuration information is transmitted to the mobileterminal periodically. In another aspect of the invention, theconfiguration information is transmitted to the mobile terminal as asystem information message on a logical channel BCCH. The configurationinformation may also be transmitted to the mobile terminal as apoint-to-multipoint control message on a logical channel MCCH.Furthermore, the configuration information may be transmitted to themobile terminal on a dedicated channel.

The configuration information may be MCCH scheduling information. Also,the configuration information may be transmitted to the mobile terminalin a system information message and a point-to-multipoint controlmessage.

In accordance with one embodiment of the present invention, a method forreceiving control information in a wireless communication systemcomprises receiving from a network configuration information forconfiguring a point-to-multipoint control channel and reading thepoint-to-multipoint control channel according to the configurationinformation. The configuration information comprises at least one of amodification period, a repetition period, a SFN-MCCH-Offset comprisingan offset between a transmission of a first frame of a modificationperiod and a system frame number (SFN) of a cell in which theconfiguration information is transmitted, and a number of transmissiontime intervals (TTIs) the mobile terminal will read at each beginning ofa repetition period.

Preferably, the configuration information is received from a radionetwork controller (RNC). The modification period is a time throughwhich critical information is not changed. The repetition period is atime between successive repetition of the transmission of critical andnon-critical information. The SFN-MCCH-Offset is an offset between a SFN0 and a first transmission of critical and non-critical information.

In one aspect of the invention, the SFN-MCCH-Offset is a multiple of 256chips and is a maximum time of a maximum modification period.Preferably, the maximum SFN-MCCH-Offset is 4096 frames.

Preferably, the configuration information is transmitted to the mobileterminal periodically. In another aspect of the invention, theconfiguration information is received as a system information message ona logical channel BCCH. The configuration information may also bereceived as a point-to-multipoint control message on a logical channelMCCH. Furthermore, the configuration information may be received on adedicated channel.

The configuration information may be MCCH scheduling information. Also,the configuration information may be received in a system informationmessage and a point-to-multipoint control message.

In accordance with another embodiment of the present invention, anapparatus for receiving control information in a wireless communicationsystem comprises means for receiving from a network configurationinformation for configuring a point-to-multipoint control channel andmeans for reading the point-to-multipoint control channel according tothe configuration information. The configuration information comprisesat least one of a modification period, a repetition period, aSFN-MCCH-Offset comprising an offset between a transmission of a firstframe of a modification period and a system frame number (SFN) of a cellin which the configuration information is transmitted, and a number oftransmission time intervals (TTIs) the mobile terminal will read at eachbeginning of a repetition period.

In accordance with another embodiment of the present invention, anapparatus for transmitting control information in a wirelesscommunication system comprises means for generating configurationinformation for configuring a point-to-multipoint control channel andmeans for transmitting the configuration information to a mobileterminal. The configuration information comprises at least one of amodification period, a repetition period, a SFN-MCCH-Offset comprisingan offset between a transmission of a first frame of a modificationperiod and a system frame number (SFN) of a cell in which theconfiguration information is transmitted, and a number of transmissiontime intervals (TTIs) the mobile terminal will read at each beginning ofa repetition period.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a block diagram of a general UMTS network architecture.

FIG. 2 is a block diagram of a structure of a radio interface protocolbetween a terminal and a UTRAN based on 3GPP radio access networkstandards.

FIG. 3 illustrates the mapping of logical channels onto transportchannels as seen by the mobile terminal.

FIG. 4 illustrates the mapping of logical channels onto transportchannels as seen by the UTRAN.

FIG. 5 illustrates possible transitions between modes and states in theUMTS network.

FIG. 6 illustrates a process of providing a particular MBMS serviceusing a multicast mode.

FIG. 7 illustrates a process of providing broadcast services.

FIG. 8 illustrates a schedule for transmitting information on an MCCH.

FIG. 9 illustrates MICH timing relative to a modification period.

FIG. 10 illustrates an Access Info period during MBMS counting.

FIG. 11 illustrates an offset between a system frame number (SFN) andthe beginning of a modification period, in accordance with oneembodiment of the present invention.

FIG. 12 illustrates MCCH configuration information being transmitted ina system information message, in accordance with one embodiment of thepresent invention.

FIG. 13 illustrates MCCH configuration information being transmitted inan MBMS control message, in accordance with one embodiment of thepresent invention.

FIG. 14 illustrates MCCH configuration information being transmitted ina system information message and an MBMS control message, in accordancewith one embodiment of the present invention.

FIG. 15 is a block diagram illustrating a mobile communication deviceincorporating the methods of the present invention.

FIG. 16 is a block diagram illustrating a UTRAN incorporating themethods of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a method for transmitting and receivinginformation for configuring a point-to-multipoint control channel in awireless communication system.

A UTRAN utilizes an MBMS Control Channel (MCCH) to periodically transmitMBMS control information to a mobile terminal. The MBMS controlinformation may include information about active MBMS services,configuration information for a traffic channel, such as MTCH, orinformation about frequency convergence, among others. The mobileterminal reads the MBMS control information on the MCCH in order toreceive MBMS services it has subscribed to based on different triggers.For example, the mobile terminal may read the MBMS control informationafter cell selection/reselection, when the mobile terminal is notifiedof a given MBMS service on MICH, or when the mobile terminal is notifiedof a given MBMS service via DCCH, among other triggers. The MCCH carriesdifferent control messages such as MBMS Common p-t-m rb Information,MBMS Current Cell p-t-m rb Information, MBMS General Information, MBMSModified services Information, MBMS Unmodified services Information,MBMS Neighbouring Cell p-t-m rb Information and MBMS Access Information.

In order to read the MCCH, the mobile terminal requires information onthe configuration of the MCCH. Thus, in accordance with one embodimentof the present invention, configuration information for configuring theMCCH is generated in the UTRAN and transmitted to the mobile terminal.In one aspect of the invention, the configuration information may beMCCH scheduling information for allowing discontinuous transmission(DTX) of data. Preferably, the configuration information comprises atleast one of a modification period, a repetition period, anSFN-MCCH-Offset, and a number of transmission time intervals (TTIs) themobile terminal will read at each beginning of a repetition period.

The modification period informs the mobile terminal of a time throughwhich critical information transmitted on the MCCH is not changed. Therepetition period informs the mobile terminal of a time betweensuccessive repetition of the transmission of critical and non-criticalinformation.

Referring to FIG. 11, the SFN-MCCH-Offset relates to an offset betweenthe transmission of a first frame of a modification period and a systemframe number (SFN) of a cell in which the configuration information istransmitted. Preferably, the SFN-MCCH Offset is the offset between anSFN 0 and a first occurrence of the broadcast of critical andnon-critical information. The offset may be in multiples of 256 chipsand correspond to a maximum time of the maximum modification period,which corresponds to the granularity of the chip offset for the RLs andS-CCPCHs in the UMTS system in one cell. The maximum SFN that can besignaled with the 12 available bits is 4095. As such, the maximumpossible modification period is 4,095 frames, i.e., 40.95 seconds.

Information transmitted on the MCCH may be carried in more than onetransmission time interval (TTI). Previously, the mobile terminal wouldcontinue receiving a physical channel carrying the MCCH informationuntil it received a TTI that did not include any MCCH data. Thus, aproblem arises because the mobile terminal reads more TTIs thannecessary. In order to optimize the reception of information on MCCH,the mobile terminal must know how many TTIs to read. Therefore, thepresent invention provides for the transmission of the number of TTIsthat the mobile terminal shall read at each beginning of a repetitionperiod. Preferably, the number of TTIs is transmitted from an RNC of theUTRAN to the mobile terminal.

Referring to FIG. 12, the configuration information may be transmittedto the mobile terminal as a system information message. Therefore, anyone or combination of, the modification period, the repetition period,the SFN-MCCH-Offset, and the number of TTIs to be read may betransmitted from the UTRAN and received by the mobile terminal through alogical channel BCCH.

Alternatively, the configuration information may be transmitted to themobile terminal as an MBMS control message, as shown in FIG. 13.Accordingly, any one or combination of, the modification period, therepetition period, the SFN-MCCH-Offset and the number of TTIs to be readmay be transmitted from the UTRAN and received by the mobile terminalthrough a logical channel MCCH.

Furthermore, the present invention also provides that the modificationperiod, the repetition period, the SFN-MCCH-Offset and the number ofTTIs to be read may be transmitted to the mobile terminal through adedicated channel. It is further provided that not all elements of theconfiguration information must necessarily be transmitted in one type ofmessage. Therefore, for example, as shown in FIG. 14, the modificationperiod, the repetition period and the SFN-MCCH-Offset may be transmittedin a system information message on a logical channel BCCH while thenumber of TTIs to be read is transmitted in an MBMS control message on alogical channel MCCH.

The following are examples including a mobile communication device and amobile communication network using the methods of the present invention.

Referring to FIG. 15, the mobile communication device 600 comprises aprocessing unit 610 such as a microprocessor or digital signalprocessor, an RF module 635, a power management module 606, an antenna640, a battery 655, a display 615, a keypad 620, a storage unit 630 suchas flash memory, ROM or SRAM, a speaker 645 and a microphone 650.

A user enters instructional information, for example, by pushing thebuttons of a keypad 620 or by voice activation using the microphone 650.The processing unit 610 receives and processes the instructionalinformation to perform the appropriate function. Operational data may beretrieved from the storage unit 630 to perform the function.Furthermore, the processing unit 610 may display the instructional andoperational information on the display 615 for the user's reference andconvenience.

The processing unit 610 issues instructional information to the RFmodule 635, to initiate communication, for example, transmit radiosignals comprising voice communication data. The RF module 635 comprisesa receiver and a transmitter to receive and transmit radio signals. Theantenna 640 facilitates the transmission and reception of radio signals.Upon receiving radio signals, the RF module 635 may forward and convertthe signals to baseband frequency for processing by the processing unit610. The processed signals would be transformed into audible or readableinformation outputted via the speaker 645. Preferably, the processingunit 610 performs the methods of the present invention. Other features,as described above in the figures, may be incorporated as well in thisembodiment.

The processing unit 610 stores messages received from and transmitted toother users in the storage unit 630, receives a conditional request formessage input by the user and processes the conditional request to readdata corresponding to the conditional request from the storage unit. Theprocessing unit 610 outputs message data to the display unit 615. Thestorage unit 630 is adapted to store message data of the messages bothreceived and transmitted.

Referring to FIG. 16, the UTRAN 700 includes one or more radio networksub-systems (RNS) 725. Each RNS 725 includes a radio network controller(RNC) 723 and a plurality of Node-Bs (base stations) 721 managed by theRNC. The RNC 723 handles the assignment and management of radioresources and operates as an access point with respect to the corenetwork. Furthermore, the RNC 723 is adapted to perform the methods ofthe present invention.

The Node-Bs 721 receive information sent by the physical layer of theterminal 600 through an uplink, and transmit data to the terminalthrough a downlink. The Node-Bs 721 operate as access points, or as atransmitter and receiver, of the UTRAN 700 for the terminal. It will beapparent to one skilled in the art that the mobile communication device600 may be readily implemented using, for example, the processing unit610 (of FIG. 16) or other data or digital processing device, eitheralone or in combination with external support logic.

Although the present invention is described in the context of a consumerproduct, the present invention may also be used in any wired or wirelesscommunication systems using mobile devices, such as PDAs and laptopcomputers equipped with wired and wireless communication capabilities.Moreover, the use of certain terms to describe the present inventionshould not limit the scope of the present invention to certain type ofwireless communication system, such as UMTS. The present invention isalso applicable to other wireless communication systems using differentair interfaces and/or physical layers, for example, TDMA, CDMA, FDMA,WCDMA, etc.

The preferred embodiments may be implemented as a method, system orarticle of manufacture using standard programming and/or engineeringtechniques to produce software, firmware, hardware, or any combinationthereof. The term “article of manufacture” as used herein refers to codeor logic implemented in hardware logic (e.g., an integrated circuitchip, Field Programmable Gate Array (FPGA), Application SpecificIntegrated Circuit (ASIC), etc.) or a computer readable medium (e.g.,magnetic storage medium (e.g., hard disk drives, floppy disks, tape,etc.), optical storage (CD-ROMs, optical disks, etc.), volatile andnon-volatile memory devices (e.g., EEPROMs, ROMs, PROMs, RAMs, DRAMs,SRAMs, firmware, programmable logic, etc.).

Code in the computer readable medium is accessed and executed by aprocessor. The code in which preferred embodiments are implemented mayfurther be accessible through a transmission media or from a file serverover a network. In such cases, the article of manufacture in which thecode is implemented may comprise a transmission media, such as a networktransmission line, wireless transmission media, signals propagatingthrough space, radio waves, infrared signals, etc. Of course, thoseskilled in the art will recognize that many modifications may be made tothis configuration without departing from the scope of the presentinvention, and that the article of manufacture may comprise anyinformation bearing medium known in the art.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present invention. The presentteaching can be readily applied to other types of apparatuses. Thedescription of the present invention is intended to be illustrative, andnot to limit the scope of the claims. Many alternatives, modifications,and variations will be apparent to those skilled in the art. In theclaims, means-plus-function clauses are intended to cover the structuredescribed herein as performing the recited function and not onlystructural equivalents but also equivalent structures.

1. A method for receiving control information in a wirelesscommunication system, the method comprising: receiving from a networkconfiguration information for configuring a point-to-multipoint controlchannel; and reading the point-to-multipoint control channel accordingto the configuration information; wherein the configuration informationcomprises: a modification period; a repetition period; a system framenumber (SFN)-multimedia broadcast multicast service (MBMS) controlchannel (MCCH)-Offset comprising an offset between a transmission of afirst frame of a modification period and a SFN of a cell in which theconfiguration information is transmitted; and a number of transmissiontime intervals (TTIs) a mobile terminal will read at each beginning of arepetition period.
 2. The method of claim 1, wherein the configurationinformation is received from a radio network controller (RNC).
 3. Themethod of claim 1, wherein the modification period is a time throughwhich critical information is not changed.
 4. The method of claim 1,wherein the repetition period is a time between successive repetition ofthe transmission of critical and non-critical information.
 5. The methodof claim 1, wherein the SFN-MCCH-Offset is an offset between a SFN 0 anda first transmission of critical and non-critical information.
 6. Themethod of claim 5, wherein the SFN-MCCH-Offset is a multiple of 256chips.
 7. The method of claim 1, wherein the SFN-MCCH-Offset is amaximum time of a maximum modification period.
 8. The method of claim 1,wherein the maximum SFN-MCCH-Offset is 4096 frames.
 9. The method ofclaim 1, wherein the configuration information is transmitted to themobile terminal periodically.
 10. The method of claim 1, wherein theconfiguration information is received as a system information message ona logical channel broadcast control channel (BCCH).
 11. The method ofclaim 1, wherein the configuration information is received as apoint-to-multipoint control message on a logical channel MCCH.
 12. Themethod of claim 1, wherein the configuration information is received ona dedicated channel.
 13. The method of claim 1, wherein theconfiguration information is MCCH scheduling information.
 14. The methodof claim 1, wherein the configuration information is received in asystem information message and a point-to-multipoint control message.15. A method for transmitting control information in a wirelesscommunication system, the method comprising: generating configurationinformation for configuring a point-to-multipoint control channel; andtransmitting the configuration information to a mobile terminal; whereinthe configuration information comprises: a modification period; arepetition period; a system frame number (SFN)-multimedia broadcastmulticast service (MBMS) control channel (MCCH)-Offset comprising anoffset between a transmission of a first frame of a modification periodand a SFN of a cell in which the configuration information istransmitted; and a number of transmission time intervals (TTIs) themobile terminal will read at each beginning of a repetition period. 16.The method of claim 15, wherein the configuration information istransmitted from a radio network controller (RNC).
 17. The method ofclaim 15, wherein the modification period is a time through whichcritical information is not changed.
 18. The method of claim 15, whereinthe repetition period is a time between successive repetition of thetransmission of critical and non-critical information.
 19. The method ofclaim 15, wherein the SFN-MCCH-Offset is an offset between a SFN 0 and afirst transmission of critical and non-critical information.
 20. Themethod of claim 19, wherein the SFN-MCCH-Offset is a multiple of 256chips.
 21. The method of claim 15, wherein the SFN-MCCH-Offset is amaximum time of a maximum modification period.
 22. The method of claim15, wherein the maximum SFN-MCCH-Offset is 4096 frames.
 23. The methodof claim 15, wherein the configuration information is transmitted to themobile terminal periodically.
 24. The method of claim 15, wherein theconfiguration information is transmitted to the mobile terminal as asystem information message on a logical channel broadcast controlchannel (BCCH).
 25. The method of claim 15, wherein the configurationinformation is transmitted to the mobile terminal as apoint-to-multipoint control message on a logical channel MCCH.
 26. Themethod of claim 15, wherein the configuration information is transmittedto the mobile terminal on a dedicated channel.
 27. The method of claim15, wherein the configuration information is MCCH schedulinginformation.
 28. The method of claim 15, wherein the configurationinformation is transmitted to the mobile terminal in a systeminformation message and a point-to-multipoint control message.